Baseline fan power calculation using the EMIT tool

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Simulation Community,

I have a question regarding the EMIT Baseline fan power calculator, a tool
provided to the energy modelers by RMI. I have used the calculator to
determine the baseline fan power. I have entered the supply airflow from
the autosized baseline model, exhaust air flow as the outside air flow and
the appropriate supply fan ratio and return fan ratio in the calculator. I
used the inputs in kW/cfm provided by the calculator in the Baseline model.
However, the SVA report is reporting higher return fan power as the model
is auto sizing the return flows higher than what the EMIT tool is using for
calculations. EMIT tool determines the return airflow by subtracting
exhaust airflow from the supply airflow. As a result when I fill out the
Section 1.4 table inputs, the calculated total fan power from the software
is higher than the Baseline allowance.

Has anyone faced similar issues when calculating the baseline fan power


*Shilpa Surana*

Shilpa Surana
shilpa surana's picture
Joined: 2015-04-22
Reputation: 0

I am not clear whether the supply fan volume is also too high or just
the return volume.

If supply volume:
- Check the SV-A to see if the altitude correction factor is 1.0. If
not, set your altitude to 0 on Project & Site -> Site Data.
- Check your system sizing ratio -- if you specify a supply flow and a
sizing ratio, the flow entered will be multiplied by the sizing ratio.

If just return volume -- you can specify a return fan volume on the flow
parameters tab of Air-Side HVAC -> Fans

bfountain's picture
Joined: 2011-09-30
Reputation: 201